Australia captain Mitchell Marsh was ruled out of their opening T20 World Cup match against Ireland in Colombo on Wednesday after being struck in the groin during training, with Steve Smith jetting in as cover.
Smith will fly to Sri Lanka as standby in case opener Marsh is unable to take any part in the tournament.
"Mitchell Marsh will miss the opening match of the ICC men's T20 World Cup after sustaining a direct blow to the groin during training earlier this week," said Cricket Australia in a statement.
"He is experiencing ongoing pain and discomfort which is restricting his movement.
"Scans have confirmed internal testicular bleeding and he will require a period of rest and rehabilitation.
"His return to play will be guided by symptom resolution and medical advice."
It is the latest injury blow to hit the Australia squad after leading pace bowlers Pat Cummins and Josh Hazlewood were forced out with injury.
The in-form Smith, one of Australia's most experienced and best players against spin, was controversially omitted from the squad despite his blistering Big Bash League form as an opening batsman.
Travis Head stood in for Marsh as Australia captain for Wednesday's game against Ireland. He won the toss and chose to bat.